Gerd Knorr wrote:
Oh-oh. Now it gets ugly. Basically I'd answer the driver may adjust one
or both, capture and overlay parameters, when the cropping rectangle is
modified. But another app causing the change is hardly acceptable. No
cropping specific problem actually, simultaneous capture and overlay may
impose all sorts of limitations. For example the same pixfmt or image
size must be used.
Is this a real issue? At least for the cards/chipsets doing overlay by
PCI-PCI transfers there is no major difference between overlay and
capture. So the crop issue is nothing really new, bttv and saa7134
already have to deal with different parameters for capture and/or
overlay set by different applications. bttv basically does that by
reprogramming the chip in the IRQ handler just before the frame gets
captured, not when the application calls S_FMT. I have to recheck the
specs, but IIRC the crop thing can be handled this way too.
Don't know that much about other hardware (usb cams?) through ...
USB doesn't support memory addressing over the bus, so that's not an
issue. IEEE-1394 does, but I don't think it's used for video purposes.
--
Mark McClelland
mark@xxxxxxxxxxxxxxxx
